Aromatic iodides are important compounds as intermediates for various electronic materials and medicinal drugs, due to high reactivity thereof. For example, developments of organic photoreceptors for electrophotography, which have a structure of laminated charge-generating layers and charge-transporting layers, have been actively promoted, and as a charge-transporting material to be used for such charge-transporting layer, various types of triarylamine compounds have been proposed (see, JP-A-5-313386), where aromatic iodides are used as an intermediate in the synthesis of such triarylamine compounds. The triarylamine compound can be synthesized by a coupling reaction of an arylamine compound with an aryl halide using a copper catalyst, and aryl iodine compounds are often used as an aryl halide. This is because use of bromide as a halogenating agent results in significantly low reactivity in the coupling reaction (conversion to tertiary amine) at final stage.
Besides the above-described use, aromatic iodides are widely used, therefore, various methods for synthesizing iodinated material of aromatic compounds have been proposed. For example, a method for iodinating an aromatic compound using iodic acid and iodine in a mixed solvent of water and acetic acid, in the presence of sulfuric acid catalyst (see, Ann. 634, 84 (1960)), a method for iodinating an aromatic compound using periodic acid and iodine in a mixed solvent of water and acetic acid, in the presence of sulfuric acid catalyst (see, J. Chem. Soc. Jap. 92, 1021 (1971)), or a method of synthesis via Sandmeyer reaction from corresponding amino compound as shown by the following scheme (see, Bull. Soc. Chem., 7, 634 (1940)):

On the other hand, when reactivity of the iodinating agent is high, or when an aromatic compound, which tends to undergo easily electrophilic substitution reaction by a functional group, is iodized, a mixture of mono-iodized product and di-iodized product is obtained, and it is sometimes difficult to obtain mono-iodized product selectively. To solve this problem, for example, a method to improve selectivity for mono-iodination by reducing molar ratio of iodine to react with an aromatic compound has been proposed (see, JP-A-7-233106). Specifically, the publication describes that when an aromatic compound is iodized using iodic acid, periodic acid or iodine as a iodinating agent in a mixed solvent of water and acetic acid, a high purity of mono-iodized product can be obtained by setting a ratio of the number of iodine atom to the number of an aromatic compound molecule to be reacted to a level less than 1, more preferably less than 0.5.
At the same time, various types of reactors are used in the production steps of these compounds. For example, emulsion concoctions have been produced using a flow reactor having a micro-structure unit such as micro-mixer with a micro-channel of, generally, several to several hundreds μm (generally, generically referred to as “micro-reactor”) (see, JP-A-2003-321325). Since emulsion concoctions influence on the quality and the like of the final product depending on the degree of homogenization, a good homogenization is obtained by using a micro-mixer, in view of the conventional technology where a sufficient effect can not be exerted due to uneven emulsified particles.
Furthermore, in carrying out Friedel-Crafts type alkylation reaction to an aromatic compound, a method for synthesizing mono-alkylated product efficiently by using a micro-mixer to improve mixing efficiency has been disclosed (see, JP-A-2004-99443). According to the application, when two kinds of liquids to be mixed are fed into a reaction vessel having a volume of several ml or more to be mixed, since assemblies of relatively large fluid clusters spreads to the whole reaction vessel coarsely, followed by diffusing by turbulent flow of vortex while becoming finer gradually and then being mixed, if mixing time is sufficiently longer than reaction time, local unevenness in concentration greatly influences on the reaction; on the contrary, since mixing occurs by molecular diffusion in a micro-channel, very rapid mixing is attained, and by using a micro-mixer, a high selectivity can be obtained.
In addition, the micro-reactor has features such as (1) heating/cooling speeds are fast, (2) flow is laminar flow, (3) surface area per unit volume is large, (4) reaction proceeds rapidly due to shorter diffusion length of material.